Thanks to the axial resisting contribution, inclined screw connections offer a mechanical advantage over connections with purely transversely loaded fasteners. However, the strong coupling between ...the axial and the transversal behaviour of the screw makes it challenging to predict the actual connection behaviour. Moreover, the presence of polyurethane interlayers for soundproofing or OSB interlayers of light-frame buildings between main members may increase the bending moment component interacting with the axial force in the screw, thus reducing the connection failure load. This paper experimentally assesses the behaviour of steel-to-timber connections, and a parametric finite element model of Winkler non-linear beam is presented and validated. Finally, a simplified analytical model for capacity prediction is presented. The results of the approach currently provided by the Eurocode 5, of an additive model and the proposed analytical model, are then compared with the results of 500 finite element analysis.
•Timber-to-steel connections with soundproofing and OSB interlayers are tested.•Interlayers reduce slip modulus more than strength.•Non-linear beam on foundation model is suitable for screws connections.•Bending moment interacts with axial force reducing the connection capacity.•An elementary capacity model is validated on 500 finite elements analysis results.
Use of timber as a construction material has entered a period of renaissance since the development of high-performance engineered wood products, enabling larger and taller buildings to be built. In ...addition, due to substantial contribution of the building sector to global energy use, greenhouse gas emissions and waste production, sustainable solutions are needed, for which timber has shown a great potential as a sustainable, resilient and renewable building alternative, not only for single family homes but also for mid-rise and high-rise buildings. Both recent technological developments in timber engineering and exponentially increased use of engineered wood products and wood composites reflect in deficiency of current timber codes and standards. This paper presents an overview of some of the current challenges and emerging trends in the field of seismic design of timber buildings. Currently existing building codes and the development of new generation of European building codes are presented. Ongoing studies on a variety topics within seismic timber engineering are presented, including tall timber and hybrid buildings, composites with timber and seismic retrofitting with timber. Crucial challenges, key research needs and opportunities are addressed and critically discussed.
This study presents an analytical method for the elastic lateral displacement calculation of platform-type cross laminated timber (CLT) lateral load resisting systems using a matrix approach. The ...current state-of-the-art models for lateral deflection calculation of single- and multi-panel CLT shear-walls systems were extended from single-storey cases to generalized multi-storey multi-panel CLT shear-wall systems. The proposed calculation method was validated against tests on twelve single-storey shear-walls and one two-storey shear-wall from four previously conducted experimental campaigns. The 2D lateral displacement analytical calculation model was then further expanded to the 3D application for CLT lateral load resisting systems through a matrix approach. The matrix method was verified against an analytical-numerical comparison on two case studies. The proposed analytical model forms a solid foundation for a potential implementation of this lateral deflection model for CLT shear-wall systems in the next generation of standards such as Eurocode 5 and CSA O86.
This study investigates timber connections with flexible polyurethane adhesives, which prove to have the potential for timber-adhesive composite structures without mechanical connections for seismic ...regions. Results of conducted cyclic double lap-shear adhesive timber joints tests were compared with available experimental results on timber connections with standard mechanical dowel-type fasteners and with results of numerical finite element analysis. The study found that the shear strength, elastic stiffness and strength degradation capacity of the flexible adhesive connections were significantly higher compared to mechanical fasteners commonly used in seismic-resistant timber connections. The latter, however, manifested larger ultimate displacements but also yielded at lower displacements.
Timber structures are widely recognized to perform very well under strong ground motions. A non-linear dynamic analysis can be carried out to assess their seismic performance for design purposes, as ...allowed by the current regulations. When dealing with timber structures, however, the difficulties typically involved by this very powerful method of analysis may increase and sometimes become even overwhelming. The reasons are mainly due to insufficient experimental data, lack of standard constitutive models for timber connections and inadequate support provided by the current seismic codes. The key aspects related to modelling the non-linear behaviour of modern timber structures with particular focus to the crucial role of connections are analyzed in this paper. By referring to a case-study building made by solid cross-laminated (X-Lam) timber panels and designed according to the Eurocodes, the path that the designer has to undertake when carrying out a time-history non-linear analysis of a X-Lam timber structure is put in evidence, while some simplified assumptions are suggested and justified. A concentrated plasticity three-dimensional model is adopted where the hysteretic behaviour of connections is implemented by exploiting experimental data available from the literature. Three suites of earthquake records are considered in the investigation. The paper aims to give structural engineers some useful hints to carry out non-linear dynamic analyses of cross-laminated timber structures for design purposes.
•Seismic performance of timber structures assessed by non-linear time-history analyses.•Modelling X-Lam buildings to perform non-linear time-history analyses for design purposes.•Concentrated plasticity 3D model of X-Lam buildings for non-linear analyses.•Ductile behaviour of X-Lam buildings under suites of severe earthquakes.•Modelling of the non-linear hysteretic behaviour of angle-brackets and hold-downs.
Almost 200 nations, including the European Union, have signed the Paris Agreement that aims to limit the temperature rise to 1.5 °C above pre-industrial levels by reducing greenhouse gas (GHG) ...emissions. To meet this target, a significant decrease in GHG emissions by 2030 and net zero by 2050 is necessary. To determine the role of wood products in achieving a 55% reduction in GHG emissions by 2030 compared with 1990 levels, we investigated Slovenia’s potential, which has close to 60% forested areas. Therefore, the country could use wood-based products to achieve the agreed-upon climate goals. Nevertheless, uncertainties remain regarding the extent to which increased tree harvesting, local manufacturing, and the utilization of wood products can aid in substituting fossil-derived materials and reducing GHG emissions. A new model was constructed to increase the understanding of the wood products’ (throughout the forest-based industrial ecosystem, incl. construction) potential contribution to reaching the stated emissions targets. Using this linear programming (LP) mathematical optimisation model and carbon footprint calculations based on life cycle assessment methods, a wood flow distribution, the financial investment needed to process these quantities, and the GHG emissions produced and/or saved were calculated. The findings stipulated that Slovenia has the potential to achieve 55 % less GHG emissions by 2030 by expanding logging to at least 3 million m3 and converting the timber to a larger amount of long service-life wooden items made (and utilised) within the country. Such products accumulate carbon for a long time and decrease the need for materials that cause higher GHG emissions. Concomitantly, a better appreciation of the substitution effects in official carbon accounting would be needed. Moreover, to materialize the potential decrease in emissions would require Slovenia’s construction sector to replace fossil- and mineral-based materials with lignocellulosic products, and to increase the capacity to utilize lower-quality wood in high added value applications, which would require significant investment. This paper offers a comprehensive analysis of diverse optimisation outcomes obtained from the investigation into climate action through the use of wood products in Slovenia.
More than one hundred ninety nations, including the European Union, have signed the Paris Agreement to limit the temperature increase to 1.5 °C above pre-industrial levels. Meeting these conditions ...requires a steep decline in greenhouse gas (GHG) emissions by the year 2030 and zero GHG emissions by 2050. In this study, we investigated the role that wood products can play within Slovenia to reach the 2030 goal of a 55 % reduction in GHG, as compared to 1990 levels. Slovenia, with over 58 % forest cover, is well-positioned to utilize wood products to meet these climate goals. However, questions exist on how increased tree harvesting and local production, and the use of wood products contribute to replacing fossil-based materials and to lower lowering GHG emissions. To better understand the importance of wood products to GHG emission reduction, this study aimed to present a model showing how the forest-based value chain (including construction) could help reach the Paris Agreement goals. We investigated the associated environmental impacts and their related economic costs. The results indicated that Slovenia could reach the 55 % GHG emission reduction goal within 2030 through increasing tree harvesting and using these resources to increase the number of durable wood products produced within Slovenia that store carbon for long periods and substitute for other high GHG emitting materials. However, realizing these potential reductions would rely on the building industry within Slovenia to replace fossil- and mineral-based materials with wood products.
AbstractA 2-story full-scale model of a cross-laminated timber (CLT) house was tested under quasi-static monotonic and cyclic loading. The primary objectives were to investigate 3D system performance ...of a CLT structure subjected to lateral loads in terms of lateral strength and deformability capacity, global behavior of the structure, frequency response of the structure before and after each test, and performance of anchoring connectors (hold-downs, brackets) and connections between CLT panels. The house was 6.0×4.8 m in plan with a height of 4.8 m. A total of five (one push-over and four cyclic) quasi-static tests were performed, one direction at a time. Parameters, such as the direction of loading, number of hold-downs, and number of screws in perpendicular wall-to-wall connections, were varied in the tests. The CLT structure performed according to the design objectives, with the ultimate resistance being almost identical in both directions. Failure mechanisms, i.e., shear failure of nails in the brackets in the first story as a result of sliding and rocking of the CLT wall panels, were similar in all tests. Even after the maximum force was reached, no global instabilities of the house were detected. Torsion effects did not compromise the integrity, stability, or the lateral resistance of the building. The outcomes of the full-scale CLT house tests will be used for further analytical and numerical analyses to help the implementation of CLT as a structural system in the North American building codes and material standards.
AbstractAn experimental program was performed at IVALSA Trees and Timber Institute on single and coupled cross-laminated (CLT) wall panels with different anchoring systems and different types of ...joints between adjacent panels. The mechanical properties of CLT walls were assessed and are critically discussed in the paper. The connector layout and the design of the screwed vertical joints were found to markedly affect the overall behavior of the structural system. The in-plane deformations of CLT panels were almost negligible, whereas concentration of forces and deformations mainly occurred in the connections. Advanced analytical models for nonlinear pushover analysis of CLT wall systems were developed and verified against test results. The models take into account all stiffness and strength components of connectors, as well as the bending and shear deformation of the panels. A parametric study of CLT wall systems with different aspect ratios and wall segmentation was performed, showing that segmentation of CLT walls decreases their stiffness and strength but significantly improves their deformation capacity.
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